Not every medicine needs a prescription. Over-the-counter drugs are those judged safe enough for people to use without a clinician's supervision, as long as they follow the label. Pain relievers, cold remedies, antacids, antihistamines, and many other products sit on open shelves in pharmacies and supermarkets. They are convenient, but they are not risk-free.

The distinction between prescription and OTC is regulatory, not pharmacological. A drug can be switched from prescription to OTC if the evidence shows it can be used safely without medical oversight. The FDA has a formal process for this, and several drugs have made the switch, including ibuprofen, loratadine, and omeprazole. Some drugs exist in both forms: a low dose for OTC use and a higher dose by prescription. This is common with NSAIDs and allergy medications.

What to keep in mind:

• Read the label. Dosage, warnings, and interactions are listed.
• Do not double up. Many OTC products contain the same active ingredient.
• Ask a pharmacist. They are trained to advise on OTC choices and interactions.
• Not for everyone. Pregnancy, chronic illness, and other medications can make OTC use risky.

Acetaminophen is a common example. Safe at recommended doses, it can cause liver failure in overdose, especially when combined with alcohol or other acetaminophen-containing products.